Conventional screw driving devices provide different ways of holding a screw in position while the screw is driven into a work material such as a wall, wood, bone, etc.
For example, one type of conventional screwdriver includes a magnetized driving bit to hold a respective metal screw to the bit during installation. Even if the magnetic driving bit can initially hold the screw perpendicularly with respect to a work material, the driving bit may have poor holding power. As a result, the screw can easily tilt to an undesirable angle when uneven force is applied on the head of the screw. Moreover, when non-ferrous screws are used, the magnetized driving bit does not serve any useful purpose as the operator must manually hold the screw in place.
Another type of conventional screwdriver includes an assembly whose mouth widens to accept and hold a screw. For example, a conventional screwdriver in U.S. Patent Publication 2009/0042164 includes an orthodontic driver tip that is configured for screwing and unscrewing an orthodontic bone screw. This conventional driver tip includes an elongated inner rod having an enlarged diameter front tip portion that widens to accept a screw head. The tip portion comprises multiple extending resilient arms, which define an opening recess. The resilient arms are pushed apart to increase a diameter of the opening and accept a screw head. A sleeve is mounted on the rod of varying diameter. A locking mechanism releasably secures the arms against lengthwise movement along the rod when the locking mechanism is moved forward to a position wherein the arms are bent into engagement with the head of a bone screw disposed inside the front tip portion.
This latter described type of conventional screwdriver also suffers from a number of drawbacks. For example, during use, a user may apply an excessive amount of force to a screwdriver to insert the screw into an object. If the screwdriver does not properly hold the screw to the tip of the screwdriver during the insertion because the assembly at the tip secures the screw using only a weak force, the screw can disengage from the driver bit assembly and potentially harm the user and/or the object into which the screw is being driven. Also, it is undesirable in certain applications such as surgery that the opening of a screw holder assembly at the tip of a conventional screwdriver must be widened to a larger diameter to release a screw head from a driving bit.